Heat olive oil in a large skillet over medium heat. Cook and stir beef in the hot oil until browned and crumbly, 5 to 7 minutes; drain and discard grease. Return skillet to heat.
Stir onion, bell pepper, celery, and carrot into the ground beef; cook and stir until the vegetables are tender, 5 to 7 minutes; add chicken gumbo soup, chili sauce, yellow mustard, and onion salt. Reduce heat to medium-low, stir beef mixture, and simmer until the sauce thickens, about 5 minutes.
